Electrical contact element



July 3,1945. qw, KETTEL 2,379,641

AELEGTRICAL CONTACT ELEMENT Filed July 21, 1942 i INVENTOR.

Af/3%@ /m/M? Vments suitable for use trical contacts of electrical" contact contact 4 has `not usually be employed l Patented July 3., 1.9 45

UNITED s'm'rlssl --PATE NTL OFFICE ELECTRICAL CONTACT ELEMENT Christian William Keitel signor to Baker & Company, Inc.,

, East Orange,` JL, as-

Newark, N. J.,

a corporation o1' New Jersey Application July 21,`1942,.SerialNo. 451,761

as well as the life of such contacts is relatively limited.

' ployment even with heavy electric currents.

l have found thatthe aforesaid objects of my invention can be attained by providing an electrical contact system wherein tact comprises silver or nickel, a ing electrical contact comprises palladium or has at least a contact .face of palladium.

The invention is illustrated in the single iigure, of the drawing representing a side view of an system comprising contact holders I and- 2 provided with electrical contacts 3 and 4.

taken from the group silver andA nickel and the a contact face of palladium.

in an electrical contact system of a contact of silver or nickel with a contact of palladium results in an electrical contact system oflong life, wherein sticking of the contacts is sub' stantially eliminated. The system of the invention may be employed, therefore, not onlywith relatively low electric currents, i. e. Icurrents of not more than 15 volts and 15 amperes, but also with relatively'heavy electric currents where contact systems of cooperating contacts oi' silver canwithout resulting diiil- The pairing culties involving sticking.

The nature and advantages of my invention are illustrated by' afew representative examples.

l In theembodiment shown in the drawing contact 3 has a contact face of metal 4 Claims. (Cl. 200-166 With an electriccurrent of 15 volts D. C. and 30.

, amp.' and after 100,000 cycles of continuous makes tact showed a loss of 0.0043

voltage drop increased from and breaks of the electric current 'an electrical contact system composed of a palladium cathode contact and a ne silver anode contact showed substantial absence of sticking and disclosed even wear of both contacts. Inv this system the l5 millivolts to 30 millivolts, the palladium contact showed a loss of 0.0022 gram," and thev system of palladium cathodecontact and nickel anode contact likewiseshowed substantial absence of sticking and disclosed even wear of both n .system the voltage drop increased from 90 millivolts to 190 millivolts, the palladium. contact showed a loss of 0.0092 gram, and the nickel congram.- As distin guished from such contact systems according to the invention, a system wherein both cooperat' ing contacts comprised fine silver showed under sionally,

' showed a gain of 0.0192 gram like operating'conditions a definite tendency to stick, anclv disclosed the formation of craters.v In this system the voltage drop increased from 3.5 millivolts to 8 millivolts, the contact cathode tact a floss of 0.0228 gram. A'system wherein both contacts comprised palladium showed under like'operating conditions a vslight tendency to stick, with the voltage drop increasing from 64 millivolts to 360 millivolts, In this system the cathode contact showed a loss of 0.0028 gram and the anode contact showed a gain of 0.0010 gram.

. It will be apparent from the above illustrationsthatl the electrical contact system of` palladium against silver' has longer life to this invention the voltagedrop remains low and the amount of metal'transferfrom one contact to the other is extremely small. It is surprising that the system palladium against silver is even more vfavorable than the system palladium against palladium, in which connection vit will be noted that such all-palladium system loses weight slightly more rapidly, has a larger metal transfer,- and higher voltage of course, the lowest voltage drop but in use becomes considerably deformed andv sticks 'occawherefor its useful life is shorter than that of the system palladium against silverpf the invention. The system of palladium against nickel is particularly suited for cases where the melting point of silver is too low and the low fine silver contact I showed a gain of 0.001 gram. A In a like experiment, an electrical contact contacts. In this and the anode conthan the system sil- 'ver against silver-in that in the system according drop than the systemof the. invention. The system silver against silver has,

-' of silver and a cathode electrical contact systems embodying one contact of silver and another contact of a metal of the platinum group other than palladium have disclosed the superiority of the system of the-inventlon embodying one contact of palladium; for instance, a system 'comprising an anode contact contact of anl alloy of '75% platinum and 25% iridium showed under like operating conditions an increase in the voltage drop from 24 millivolts to 210 millivolts,A a loss of 0.0028 gram for the platinum contact, and of 0.0024 gram for the silver contact.

The electrical contact system according to the invention is useful not only in D. C. operations, but also in A. C. operations where such system of the invention, likewise,4 stick and exhibits a tem silver against silver. i

The terms sllver, palladium and nickel as herein used shall include not only pure metals but also such other compositions wherein such metals predominate, although it will be under- Y, stood that contacts of the pure metals are to be generally preferred; The determining factor in the electrical contact system according to the indisplays less tendency to c longer useful life than the sys- -the contacts consist in their entiretyA of such metals. Y

WhatIclaimis:` i

' l. Electrical contact system for making and breaking electric current, comprising a pair of cooperating electrical contacts site each other wherein one such electrical con- ,tact has a contact face of metal taken from the group silver and nickel, and the other electrical contact has a contact face of palladium.

2. Electrical contact system for making and Abreaking electric current, comprising a pair of cooperating electrical contacts positioned opposite each other wherein one such electrical contact has a contact face of silver and the other electrical contact has a contact face of palladium.

3. Electrical contact system for making and breakingelectric current, comprising a pair of cooperating electrical contacts positioned opposite each otherywherein the anode contact has a contact face of silver andthe cathode contactv has a contact face of palladium.

4. Electrical contact system for making and breaking electric current, comprising a pair oi cooperating electrical contacts positioned opposite each other wherein one such electrical convention is the requirement that the contact faces,

i. e. thecontacting surfaces, consist of silver, palladium, and nickel, respectively, and it -will be understood, therefore, that it is not necessary that tact has a contact face of fine silver and the other electrical contact has a contact face of pure palladium.

' CIEIRISTIAN WILLIAM KEITEL.

positioned oppor I' 

